Chronic zinc (Zn) deficiency is a major public health issue affecting over two billion people, particularly women and children in developing countries. The main reason of human Zn deficiency is low dietary intake due to heavy reliance on staple crops (i.e. wheat, rice and maize) which are inherently low in Zn and other micronutrients. Agricultural strategies offer a practical and cost-effective solution to the problem by increasing the grain Zn concentration of cereal crops through breeding (genetic biofortification) and fertilization (agronomic biofortification) approaches. Agronomic biofortification provides an instant solution to the problem by applying Zn-containing fertilizers to soil and/or plant as a foliar spray.

This project was devoted to reveal the individual and combined effects of genetic and agronomic Zn biofortification in wheat and maize. The first part focused on understanding the mechanisms involved in differences in uptake and translocation of foliar-applied Zn among wheat and maize species by using 70Zn, a stable isotope of Zn. It was shown that wheat has a greater capacity of leaf uptake and translocation of foliar-applied Zn compared to maize. The second part studied the effectiveness of Zn fertilizer applications in the form of soil, foliar and soil + foliar for improving growth, grain yield and nutrients uptake by genetically biofortified HarvestPlus wheat genotypes developed through long term breeding activities at CIMMYT. The results confirmed that the genetically biofortified HarvestPlus wheat genotypes have higher capacity to uptake, utilize and translocate Zn from soil and/or foliar applications more efficiently as compared to non-biofortified conventional cultivars. The third part investigated the effect of nitrogen (N) supply on uptake and accumulation of Zn in maize and wheat. Improving N supply significantly enhanced root uptake and shoot translocation as well as leaf uptake of Zn from foliar Zn sprays in wheat and maize. These results conclude that the best strategy to improve grain Zn accumulation while maintaining higher yields to tackle human Zn deficiency involves an integrated approach of cultivating genetically biofortified cultivars of maize and wheat with sufficient soil and foliar Zn applications.